1. Field of the Invention
The present invention pertains to rotary power brushes of the street sweeping broom type, and more particularly, it pertains to an improved helically coiled brush strip which can be maintained in a tight non-slip condition upon the cylindrical surface of a broom core member under both brushing load and unloaded conditions.
2. Description of the Prior Art
A typical construction for a rotary power brush, such as might be used on street sweepers for example, comprises a generally cylindrical core member about which a helical brush strip is tightly wrapped. The brush strip includes a channel element having a tightly bunched, continuous series of reversely bent bristles secured therein. The bristles are arranged to be secured within the channel at their bight portions by means of an anchoring wire or cable which extends the full length of the brush strip.
In one rotary brush construction of the afore-described type that is widely used in the street sweeper industry and is shown in prior U.S. Pat. No. 3,193,866 to Jones, one end of the brush strip is fastened to the core by means of a slack accumulator device which comprises a flexible cable attached to the end of the brush strip and to the end face of the core so as to allow the brush strip to rotate in one direction if slack develops along the length thereof but preventing it from rotating in the opposite direction wherein it would unwind from the core. When slack does develop in the brush strip, the attachment of the aforementioned cable to the end face of the core can be loosened, and the brush strip can be pulled tighter about the core to remove such slack before reclamping the cable to the core. Thus, by means of periodic manual take-up of the slack in the brush strip, the brush strip can be maintained in a tightened condition on the core.
In the aforementioned prior art rotary coiled brush construction as shown in U.S. Pat. No. 3,193,866, it was found to be necessary to provide a fixed helical guide track upon the surface of the core for receiving the coiled brush strip in order to maintain the coils of the brush strip in the proper spaced relationship and thereby achieve a good brushing action with the broom. If the track were not provided, any slackness which developed in the brush strip might result in a spreading of certain adjacent coils which would leave an undesirable streak in the brushed strip of road surface or pavement.
Attempts to improve this basic rotary coil brush construction and overcome the foregoing problem are disclosed in the recently issued U.S. Pat. No. 3,750,225 to Gould et al, and in my pending patent application Ser. No. 491,021, assigned to the assignee of the present application. The rotary brushes described and shown in these patent disclosures also include a helical brush strip which is arranged to be tightly secured about a cylindrical core. However, no guiding channel means are provided upon the cylindrical surface of the core for holding the brush strip coils in place. Instead, one or both ends of the brush strips are provided with one-way clutch or ratchet-type devices which provide for an automatic positive take-up of any slack in the brush strips as soon as it occurs. Thus, the need for the guide channel is allegedly obviated since the automatic take-up provided by the brush strip mounting means will maintain the brush strips in tight engagement with the cores at all times.
It has been found, however, that the automatic take-up devices do not always function as intended, and, particularly in those cases wherein the core is perfectly cylindrical, a certain amount of slack can develop during the removal of the sweeping load which can lead to an axial shifting of one or more coils upon the cylindrical face of the core. Thus, it has been found to be sometimes necessary to utilize auxiliary guide and spacing means for maintaining a fixed spacing of the coils of the brush strip (particularly at the end coils) so that they will not shift axially on the core during the use of the broom. Such means has heretofore included the use of a clip removably secured to the core which must be removed before the brush strip can be replaced on the core, and such removal has proven to be both a difficult and disagreeable job.